1. Field of the Invention
The present invention relates in general to metallic cooking vessels such as pans and pots and, more particularly, to a stainless steel cooking vessel whose base bottom is added, using a pressing device such as a friction press or a high-frequency heating device, with a copper, copper alloy, aluminum or aluminum alloy bottom plate for improving its heat transfer rate.
2. Description of the Prior Art
Conventionally, a metallic cooking vessel such as a fry pan or a stew pot is mainly made of a stainless steel suitable for keeping the vessel from rusting. The base bottom or a stainless steel base bottom of such a cooking vessel is preferably added with a copper, copper alloy, aluminum or aluminum alloy bottom plate on its outer surface for improving its heat transfer rate. An additional stainless plate is joined to the outer surface of the bottom plate for forming an outermost bottom layer of the cooking vessel. This outermost bottom layer prevents possible damage and possible rust of the frail bottom plate. The joining of the additional stainless steel plate to the bottom plate may be achieved by a pressing device such as a friction press using instantaneous pressure. Alternatively, the joining of the additional stainless steel plate to the bottom plate may be achieved by high-frequency heating using a solvent such as powder or flux. Hence, the above cooking vessel has a triple bottom structure comprising the stainless steel base bottom, the bottom plate added to the base bottom and the additional stainless steel plate joined to the bottom plate. In this regard, the above cooking vessel is named as a triple bottom structure cooking vessel.
However, such a cooking vessel having the triple bottom structure uneconomically wastes the copper, copper alloy, aluminum or aluminum alloy for the bottom plate and this causes increase of the cost.
The above cooking vessel should be used with specified heating devices, so that it is inevitably limited in its use.
The outermost bottom surface of the cooking vessel or the outer surface of the additional stainless steel plate is formed of the same material, that is, the stainless steel, and shows a simple flat surface. This cooking vessel thus has a bad heat reception structure at its bottom due to the flat bottom surface. In this regard, when the vessel is laid on and heated by a heating device such as a gas range, the flames of the heating device contact with and heat the flat bottom surface of the vessel and in turn pass by the bottom corner of the vessel in order to disappear into the atmosphere. This causes considerable heat loss and waste of fuel. Furthermore, the flames of the heating device heat intensively the single-layered bottom corner of the cooking vessel while passing by this bottom corner, so that the food in the vessel gets partially scorched about and sticks to the bottom corner.
Since the outer bottom of the above cooking vessel is made of the same material and has a simple flat surface, the vessel shows no good outer appearance when it is not used but kept turned over. The bad outer appearance of the bottom surface deteriorates value of the vessel.